Brake drum with dust-guiding groove for guiding brake dust towards a brake dust collector

ABSTRACT

The invention relates to a brake drum for a vehicle drum brake,
         the brake drum comprising:   an inner circumferential surface that extends around a rotation axis and that is configured to be contacted by a brake shoe for generating a braking effect; and   a brake dust collector;   wherein at least one dust-guiding groove is provided in the circumferential surface and extends towards the brake dust collector.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims priority under 35 U.S.C. § 119to German Patent Application No. 102022206245.0, filed on Jun. 22, 2022in the German Patent and Trade Mark Office, the disclosures of which areincorporated herein by reference.

TECHNICAL FIELD

The invention concerns a brake drum for a drum brake of a motor vehicle,such as a car, a truck or a bus.

BACKGROUND

Drum brakes are an established braking technology for motor vehicles.They typically comprise a brake drum having a contact surface at aninner circumferential face and a backing plate carrying brake shoeswhich have a friction lining for contacting the contact surface. Anexample can be found in KR 2006 006 3092 A.

There remains room for improvement with respect to the levels of brakedust that are emitted into the surroundings. Upon braking, the abrasivecontact between the friction lining and contact surface generates brakedust. The brake dust can soil the brake drum itself as well as adjacentvehicle components. Also, it can be emitted into the surroundings,thereby polluting the environment. Accordingly, attempts have been madeto limit the levels of emitted brake dust, e.g. by providing adust-tight casing which encloses the brake drum. Yet, such solutionsincrease costs and weight.

SUMMARY

It is therefore an object of this invention to improve the brake drumfor a drum brake of a motor vehicle with respect to its brake dustemissions.

This is object is achieved by a brake drum and a method according toclaim 1. Advantageous embodiments are defined in the dependent claims aswell as in this description and in the figures.

Accordingly, a brake drum for a vehicle drum brake is suggested, thebrake drum comprising:

-   -   an inner circumferential surface that extends around a rotation        axis and that is configured to be contacted by a brake shoe for        generating a braking effect; and    -   a brake dust collector;        wherein at least one dust-guiding groove is provided in the        circumferential surface and extends towards the brake dust        collector.

Terms such as axial, radial and circumferential used herein may relateto the rotation axis. An axial direction may extend along said axis, aradial direction may extend orthogonally thereto and a circumferentialdirection may extend about said axis.

The brake drum may comprise a homogeneous drum member (e.g. with respectto its material) and/or a one-piece drum member. This drum member maydirectly comprise the inner circumferential surface in which thedust-guiding grooves are formed. As detailed below, the drum member mayalternatively carry a friction ring comprising said innercircumferential surface.

The brake drum and in particular its optional drum member may comprise aring section extending concentrically about a rotation axis. The ringsection may be circular. It may define a cylindric section, inparticular a cylinder mantel surface or cylinder jacket (e.g. a cylinderwithout base surfaces). The ring section may define an outer and/orinner circumferential face of the brake drum and may comprise the innercircumferential surface in which the dust-guiding groove is formed. Thering section may define a largest diameter of the brake drum.

The brake drum and in particular its optional drum member may comprise acircular wall section extending at an angle to the rotation axis. Thewall section may be plate- or disc shaped and/or may be substantiallyplanar. It may extend orthogonally to the rotation axis. It may mergewith and/or into the ring section. The ring section may extendorthogonally to the wall section. The wall section may extendconcentrically with respect to the rotation axis.

The wall section may comprise a connection portion for connecting thebrake drum to an axle component and/or to a vehicle wheel. The brakedrum may generally be configured to rotate jointly with the axlecomponent and/or the vehicle wheel. The connection portion may be a hubportion. It may comprise a least one through-hole, e.g. for receiving amechanical fixing element (e.g. a bolt). The connection portion may bepositioned at the wall section and/or may comprise a geometric center ofthe wall section. It may be intersected by the rotation axis.

The wall section may form a base surface of a cylinder, the mantle ofwhich is formed by the ring section. The brake drum may be formed as acylinder that is open to one side, e.g. by missing a base surfaceopposite to the wall section.

The brake dust collector may be arranged at the wall section. It may bearranged at an inner face of the wall section that faces towards theinner circumferential surface and/or merges with said innercircumferential surface.

The brake dust collector may be a planar member and in particular adisc-shaped member. It may comprise a structured (in particularnon-smooth) surface that is e.g. rough, porous or otherwise opened.Additionally or alternatively, said surface may comprise edges,projections, recess and/or undercuttings. These structural features mayhelp to catch and collect brake dust particles.

Additionally or alternatively, the brake dust collector may comprise anadhesive material, e.g. an adhesive layer or an adhesive coating towhich brake dust particles may adhere.

The brake dust collector may be removably connected to the brake drum,e.g. by being mechanically fixed thereto (e.g. by means of clamps,screws or a force fit) or by being adhered thereto. This way, the brakedust collector can be replaced to restore a dust collecting capabilityof the brake drum.

The dust-guiding groove may generally be configured to guide brake dusttowards the brake dust collector. Specifically, it may be configured toguide the brake dust from its place of origin at the innercircumferential surface towards the brake dust collector. Said brakedust collector may generally be close to but arranged separately fromand e.g. next to the inner circumferential surface.

The dust-guiding groove may also be referred to as a dust-guiding slot,a dust-guiding recess or a dust-guiding channel. The dust-guiding groovemay be formed by an elongated cut-out section of material that isremoved from the brake drum. The dust-guiding groove may be open on itsradially inner side (i.e. the side that faces the rotation axis). Otherthan that, it may have closed sidewalls and/or may e.g. have across-section that is only open on said radially inner side.

The dust-guiding groove may have at least one open axial end face thate.g. opens into the surroundings of the brake drum and/or faces thebrake dust collector. Alternatively, at least one axial end portion maybe located within the inner circumferential surface. It may define aregion of a gradually decreasing depth and/or a ramped or levelling-offend portion of the dust-guiding groove.

In one example, the groove has a depth (e.g. measured in a radialdirection and/or relative to the inner circumferential surface) of atleast 0.5 mm, at least 1 mm or at least 3 mm. This has been found toprovide a reliable dust guiding function. On the other hand, the depthmay not be larger than 10 mm, not larger than 20 mm and not larger than50 mm. While such a depth may still provide benefits in terms of dustguidance, it could unduly weaken the structure of the brake drum.

A width of the groove that is e.g. measured orthogonally to the depthand orthogonally to a longitudinal axis of the groove may e.g. bebetween 2 mm and 50 mm A length of the groove may be at least 10 cm ormay be at least 20 cm, but may be smaller than a circumference of theinner circumferential surface (or smaller than 1.5 times saidcircumference). Generally, a larger length may increase the chances ofcollecting dust in the groove and guiding it towards the brake dustcollector. On the other hand, the increased length may structurallyweaken the brake drum and/or occupy a respectively increased share ofthe area of the inner circumferential surface. This share is notavailable for brake force generation when being contacted by a brakeshoe.

Accordingly, according to one embodiment, a share of the surface area ofthe inner circumferential surface in which the dust-guiding grooveextends (and in particular in which all dust-guiding grooves of anoptional plurality extend) may be below 20% and in particular below 10%or below 5%.

The suggested brake drum arranges a brake dust collector directly withinthe suggested brake drum, so that brake dust emissions into thesurroundings may be limited.

Also, by providing the dust-guiding groove, the share of generated brakedust that is collected by the brake dust collector may be increased. Thedust-guiding groove can be simple to produce, e.g. directly whencasting, forging or machining the brake drum.

Further, the dust-guiding groove helps to reduce weight and introduces asurface structure that can help to limit the generation of brake noises.Specifically, the dust-guiding groove may help to absorb or otherwisedisturb soundwaves which may thus no longer contribute to generatedacoustic brake noises.

Still further, the dust-guiding groove can be used as a design parameterfor adjusting the dynamic behaviour (i.e. the vibration characteristics)of the brake drum in a desired manner. For example, it can generally bedesired to set the eigenfrequencies of the brake drum clearly apart fromother brake components and/or adjacent vehicle components to limitvibrational couplings therewith. By positioning, sizing and shaping thedust-guiding grooves appropriately, a respective adjustment of theeigenfrequencies is possible, in particular without adding additionalmasses or a complex redesigns of the brake drum's overall shape.

According to a further embodiment, the dust-guiding groove extends froma first end portion at a first axial distance to the brake dustcollector to a second axial end portion that is axially closer to thebrake dust collector. Accordingly, the dust-guiding groove may generallybe configured to guide brake dust from regions that are at an axialdistance to the brake dust collector towards the brake dust collector.

In one example, the dust-guiding groove has a non-linear course. Forexample, the dust-guiding groove may have a bent or curved course ase.g. defined by a longitudinal axis of said groove. Nonetheless, alinear course can be provided as well, this linear course e.g. beingnon-horizontal and/or non-vertical and/or run diagonally along the innercircumferential surface and towards the brake dust collector.

According to a further aspect, the dust-guiding groove extends along thecircumferential surface while covering a circumferential distance aswell as an axial distance, thereby achieving a reliable dust guidancetowards the brake dust collector.

In one example, the dust-guiding groove defines at least a segment of ahelix and/or may be helix-shaped. This helps to prevent sharp edges orangles that could locally increase mechanical stresses. Also, this helpsto increase a length of the dust-guiding groove at limited axialdimensions. A slop of said helix may be constant or may vary along itslength.

Generally, a plurality of dust-guiding groove may be provided. At leastsegments of a dust-guiding groove, in particular one or both endsections, may be arranged at an angular distance to another dust-guidinggroove. The angular distance may e.g. be between 20° and 180°).Increasing the number of dust-guiding grooves may increase the brakedust guiding capability and thus brake dust collecting capability of thebrake drum.

In one example, there are at least two dust-guiding grooves which, atleast in one segment, extend next to and/or along and/or in parallel toone another. Put differently, a first dust-guiding groove having a firstsegment and a second dust-guiding groove having a second segment may beprovided, wherein the first and second segment extend next to and/oralong and/or in parallel to one another.

When a plurality of dust-guiding grooves is provided, the dust-guidinggrooves may be sized and shaped similarly. Yet, at least segmentsthereof may be circumferentially offset relative to one another. Forexample, each dust-guiding groove may have a similar course, e.g.defining a helix-segment, but may start from an individualcircumferential position. Thus, a plurality of circumferentially spaceddust-guiding grooves may be provided forming in particularcircumferentially spaced helix segments.

According to another embodiment, the circumferential surface iscomprised by a friction ring that is arranged at an innercircumferential face of a drum member of the brake drum. In this case,the brake drum may have a multi-part design with at least the drummember and friction ring formed as separate, yet connected members. Thefriction ring may e.g. be mechanically connected to the drum member ormay be welded or glued thereto. Such multi-part design of the brake drummay be beneficial in that the friction ring can be specifically adaptedto interact with the brake shoes. The drum member, on the other hand,can have a primarily carrying and/or stabilising function, thus e.g.being made of a cheaper material compared to the friction ring.

Alternatively, the circumferential surface may be comprised by a drummember of the brake drum, the drum member e.g. being the only member ofthe brake drum (i.e. the brake drum having a one-piece design). This mayreduce production and assembly costs.

In one embodiment, the brake dust collector is arranged in or at asurface of the brake drum extending at an angle to the rotation axis, inparticular wherein the brake dust collector is arranged at a (preferablycircular) wall section of the brake drum discussed above. Said wallsection may form a base surface of the brake drum.

The brake dust collector may e.g. be adhered to said surface ormechanically fixed to said surface and form a layer on top of andprotruding relative to said surface. The surface may generally be planarand/or smooth. Alternatively, the surface may comprise a recess in whichthe brake dust collector is at least partially received, e.g. ispartially countersunken.

According to a further aspect, the brake dust collector may comprise atleast one of:

-   -   a mesh, in particular a metallic mesh or plastic mesh;    -   an adhesive, in particular an adhesive surface or an adhesive        coating or an adhesive layer;    -   a fabric, e.g. comprising a plastic textile material or natural        textile material, such as cotton.

The mesh and fabric may provide a structured surface for catching dust.They may optionally be coated with an adhesive.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the invention are discussed below with respect to theattached schematic figures. Throughout the figures, same or similarfeatures may be marked with same reference signs.

FIG. 1 is a cross-sectional partial view of a brake drum according to afirst embodiment of the invention.

FIG. 2 is a front view of the brake drum of FIG. 1 .

FIG. 3 is a cross-sectional partial view of a brake drum according toanother embodiment of the invention.

FIG. 4 is a front view of the brake drum of FIG. 3 .

FIGS. 5-8 show variants of the dust-guiding groove according to furtherembodiments of the invention.

FIGS. 9-11 show variants of the brake dust collector according tofurther embodiments of the invention.

DETAILED DESCRIPTION

FIG. 1 is a cross-sectional view of one half of a brake drum 10 that isdesigned according to an embodiment of the invention. The brake drum 10is configured to rotate about a rotation axis R. The rotation axis formsan axis of symmetry of the brake drum 10, the brake drum 10 also beingconcentric to said rotation axis R.

The brake drum 10 comprises a hub portion 12 for being coupled to anon-illustrated vehicle wheel and/or a rotating axle component of thevehicle. As an optional feature, the hub portion 12 comprises a numberof off-centre through holes 13 for receiving mechanical fixing elements,such as bolts, for being secured to the axle component and/or to thevehicle wheel. In the embodiment of FIG. 1 , the brake drum 10 is aone-piece member having an integrated drum member 14 made of a metallicmaterial, such as cast iron.

The brake drum 10 comprises a circular wall section 16 that is plateshaped an extends at an angle to the rotation axis R. For example, thewall section 16 extends at an angle of more than 60° or more than 80° tothe rotation axis R and may substantially extend orthogonally to therotation axis R. At its geometric centre that is intersected by therotation axis R, the wall section 16 comprises the hub portion 12.

The brake drum 10 also comprises a ring section 18. The ring section 18is configured as a section of a cylinder mantle surface that isconcentrically positioned with respect to and extends about the rotationaxis R. The wall section 16 merges with the ring section 18 and extendsat an angle thereto.

Said angle may e.g. amount to at least 60° or more than 80° and/or thewall section 16 may substantially extend orthogonally relative to thering section 18. The ring section 18 extends substantially axially. Ithas a ring-shaped axial end face 19 forming an outer edge of the ringsection 18.

At its inner circumferential surface 20, the ring section 18 has ametallic contact surface for being contacted by a non-illustrated brakeshoe to generate a braking effect. In a generally known manner, thebrake shoe may be configured to carry a non-illustrated friction liningthat comprises a friction material. This friction material may beabraded when contacting the inner circumferential surface 20, therebygenerating brake dust.

The wall section 16 forms a base surface of the drum member 14. At itsinner face 17 which faces an interior of the drum member 14 and which isoriented towards the inner circumferential face 20, a brake dustcollector 22 is provided. The brake dust collector 22 can be configuredaccording to any of the examples disclosed herein, e.g. can comprise atextile material and/or a mesh and/or an adhesive substance.

The brake dust collector 22 is configured as a ring-shaped memberextending concentrically with respect to the rotation axis R. It issecured at the inner face 17 of the wall section 16 according to any ofthe examples discussed in connection with FIGS. 9-11 below. The brakedust collector 22 has a non-obstructed surface facing away from theinner face 17 and towards the interior of the drum member 14 as well astowards the inner circumferential face 20. Brake dust may be collectedat said surface.

The inner circumferential surface 20 comprises a number of dust-guidinggrooves 24. The dust guiding grooves 24 extend along at least a part ofthe circumferential surface 22 towards the brake dust collector 22. Theyare open towards the inside of the drum member 14, i.e. have a radiallyinner open face. They define elongated slots or recesses within theinner circumferential surface 20. By way of their open face, brake dustcan enter each dust-guiding groove 24 and be guided along and withinsaid dust-guiding groove 24 towards the brake dust collector 22. Thismay be supported by centrifugal forces resulting from a rotation of thebrake drum 10.

The number of said dust-guiding grooves 24 in any of the depictedembodiments is merely exemplary and more or less dust-guiding grooves 24may be provided. Also, the size of the dust-guiding grooves 24 and inparticular its size relation to the drum member 14 is merely schematic.The dust-guiding grooves 24 can be significantly smaller than depicted(e.g. less wide and/or less deep).

The positioning and extension of the dust-guiding grooves 24 is alsodiscussed in the following with reference to FIG. 2 . FIG. 2 is a frontview of the brake drum 10 of FIG. 1 , so that the rotation axis Rextends orthogonally to the image plane. A number of dust-guidinggrooves 24 and specifically of first end portions 25 thereof is visiblein FIG. 2 , not all of which are marked by an own reference sign. As amere example, these end portions 25 open into the surroundings, thusforming an outwardly opened end section of each dust-guiding groove 24.For doing so, the end portions 25 form cutouts in the axial end face 19of the ring section 18. This, however, is not mandatory. Alternatively,the dust-guiding grooves 24 can have a respective first end portion 25located within the inner circumferential surface 20 and at an axialdistance to the axial end face 19 of the ring section 18. In this case,the end portions 25 may form dead ends or blind ends of eachdust-guiding groove 24, but may be positioned similarly and inparticular may be a circumferentially distributed similarly to theexample of FIG. 2 .

In more detail, FIG. 2 shows that the end portions 25 of thedust-guiding grooves 24 are circumferentially spaced apart from oneanother. In particular, they are regularly spaced apart with angulardistances between the respectively adjacent end portions 25 beingconstant.

Starting from an end portion 25, each dust-guiding groove 24 has anextension along the inner circumferential face 20 resembling ahelix-segment. This type of extension is identical for each dust-guidinggroove 24 while maintaining the circumferential spacing between thedust-guiding grooves 24. Therefore, when e.g. viewed in an axialdirection, a sequence of curved dust-guiding grooves 24 defininghelix-segments extends within the inner circumferential surface 20 andspecifically from the axial end face 19 towards the brake dust collector22.

In the cross-sectional view of FIG. 1 , a number of dust-guiding grooves24 is included. These dust-guiding grooves 24 are cut at differentpositions along their length. Only the rightmost dust-guiding groove 24has its end portion 25 located directly in the sectional plane. Theother dust-guiding grooves 24 are cut at a position remote from theirrespective end portion 25 (which are not comprised by the sectionalplane).

A dashed line schematically illustrates the course of each dust-guidinggroove 24 towards the brake dust collector 22 and along the innercircumferential face 20. This course is only highly schematicallyindicated by the dashed lines and can be curved according to theunderlying helix shape. Nonetheless, it can be seen that thedust-guiding groove 24 extend next to and along one another from theaxial end face 19 towards the brake dust collector 22.

Also, a second end portion 23 of the dust-guiding grooves is marked atwhich the dust-guiding grooves 24 open towards the brake dust collector22. From FIG. 1 , it can be seen that each dust-guiding groove 24 thuscovers an axial distance and in particular the axial distance betweenthe end face 19 and the brake dust collector 22.

From FIG. 1 , it is also apparent that the inner circumferential surface22 is part closed and smooth for the most, i.e. is free of thedust-guiding groove 24. The dust-guiding groove 24 only make up for oroccupy less than 10% of the total surface area of the innercircumferential surface 22. Thus, there remains a sufficiently largeshare of the inner circumferential surface 22 that can be contacted bynon-depicted brake shoes for generating brake forces.

FIGS. 3 and 4 are views similar to those of FIGS. 1 and 2 and depict abrake drum 10 according to a second embodiment. The difference to thefirst embodiment concerns the brake drum 10 being a multi-part assembly.More precisely, the inner circumferential surface 20 in which thedust-guiding recess 24 are formed is comprised by a friction ring 26.The friction ring 26 is inserted into and fixed to a drum member 14 ofthe brake drum 10 and specifically to an inner circumferential face 21of the drum member 14. It is also evident from FIG. 4 that the spacing,dimensioning and extension of the dust-guiding grooves 24 is identicalto FIG. 1 , with the dust-guiding grooves 24 extending within and alongthe inner circumferential surface 22 of the friction ring 26.

FIGS. 5 to 8 illustrate possible variants of the dust-guiding grooves 24according to further embodiments. Only part of the brake drum 10 isillustrated in these figures (and also in the subsequent FIGS. 9-11 )but the brake drum 10 can generally be designed similar to the one ofFIGS. 1-2 .

The depicted number of dust-guiding grooves 24 is merely exemplary andmay be higher or lower. Also, FIGS. 5 to 8 show dust-guiding grooves 24being directly formed in the drum member 14 similar to the embodiment ofFIGS. 1 and 2 . However said dust-guiding grooves 24 can be provided ina friction ring 26 according to the embodiment of FIGS. 3 and 4 as well.

In FIG. 5 , the dust guiding grooves 24 have a triangular cross-sectionwith one side of the triangle being open towards the interior of thebrake drum 10. In FIG. 6 , the dust-guiding grooves 24 have a roundedand in particular a dome-shaped cross-section. Alternatively, a roundedcross-section could be half-circular or half-elliptic. In FIG. 7 , thedust-guiding grooves 24 have a rectangular cross-section, whereas inFIG. 8 the cross-section is trapezoidal.

FIGS. 9-11 shows variants of arranging the brake dust collector 22(again only part of which is visible) in the brake drum 10. In FIG. 9 ,the brake dust collector 22 is a separate member, e.g. a mesh or aporous disc, and is attached to a generally smooth and planar inner face17 of the wall section 16 of the brake drum 10.

In FIG. 10 , the inner face 17 comprises a recess 28 in which the brakedust collector 22 is received, in particular so as to be flush withadjacent surfaces of the brake drum 10.

In FIG. 11 , the brake dust collector 22 is a coating, in particular anadhesive coating, that is applied to the smooth and planar inner face17. Alternatively, the brake dust collector 22 may be a removableadhesive disc that adheres to said inner face 17.

What is claimed is:
 1. Brake drum for a vehicle drum brake, the brakedrum comprising: an inner circumferential surface that extends around arotation axis and that is configured to be contacted by a brake shoe forgenerating a braking effect; and a brake dust collector; wherein atleast one dust-guiding groove is provided in the inner circumferentialsurface and extends towards the brake dust collector.
 2. Brake drumaccording to claim 1, wherein the dust-guiding groove extends from afirst end portion at a first axial distance to the brake dust collectorto second axial end portion that is axially closer to the brake dustcollector.
 3. Brake drum according to claim 1, wherein the dust-guidinggroove has a non-linear course.
 4. Brake drum according to claim 1,wherein the dust-guiding groove extends along the circumferentialsurface while covering a circumferential distance as well as an axialdistance.
 5. Brake drum according to claim 1, wherein dust-guidinggroove defines at least a segment of a helix shape.
 6. Brake drumaccording to claim 1, wherein at least two dust-guiding grooves areprovided which, at least in one section of the inner circumferentialsurface, extend next to one another.
 7. Brake drum according to claim 1,wherein the inner circumferential surface is comprised by a frictionring that is arranged at an inner circumferential face of a drum memberof the brake drum.
 8. Brake drum according to claim 1, wherein thecircumferential surface is comprised by a drum member of the brake drum.9. Brake drum according to claim 1, wherein the brake dust collector isarranged in or at a surface of the brake drum that extends at an angleto the rotation axis, in particular wherein the brake dust collector isarranged at a wall section forming a base surface of the brake drum. 10.Brake drum according to claim 1, wherein the brake dust collectorcomprises at least one of: a mesh, in particular a metallic mesh; anadhesive; a fabric.